1. Field of the Invention
This invention relates to an automatic stopping mechanism for a tape feeding device for detecting stopping of rotation of a reel receiver by an end of a tape to stop a tape driving source and return an operation mode setting operating member to its home position.
2. Description of the Prior Art
An automatic stopping mechanism for a tape feeding device such as, for example, a tape recorder or a VTR (video tape recorder) is already known wherein stopping of rotation of a reel receiver by an end of a tape is detected to release an operation mode of the tape feeding device such as a reproducing (PLAY) mode.
A conventional automatic stopping mechanism for a tape feeding device is designed to detect an end of a tape from a change in tension of the tape. In particular, a tape tension detecting arm (tension arm) is mounted on a support plate on which a magnetic head is supported. The tension arm presses at an end thereof against a magnetic tape and locally bends the tape while it is being fed.
In the reproducing (PLAY) mode or the recording (REC) mode, when a tape comes to its end, the tape is strained so that the tension thereof increases suddenly. Consequently, a portion of the tape which has been locally bent now tries to stretch itself straight to push the tension arm back to its inoperative home position. The movement of the tension arm then is utilized to stop a tape driving source or the like and allow an operating member for the reproducing mode or the like to return to its home position.
However, such a conventional automatic stopping mechanism wherein a tension arm is employed has following drawbacks:
At first, a tape is damaged readily because it is fed along a locally bent path while it is held pressed by the tension arm. Further, since the resistance to the tape being fed is increased by the tension arm, the force to contact a pinch roller with a capstan must necessarily be increased accordingly. However, increase of the contacting force of the pinch roller will cause a higher lateral pressure to act upon the capstan. Accordingly, the capstan must necessarily be mounted more firmly, which makes designing of bearing means for the capstan complicated.
Secondly, because a tape is fed along a locally bent path, such feeding of the tape is not stabilized, and such unstableness of feeding of the tape appears notably particularly at a join or the like of the tape. The unstableness of tape feeding has a significant influence on reproduction and recording characteristics so that it may become difficult to attain high performances of reproduction and recording of the tape feeding device because the tension arm is mounted on the support plate for the magnetic head and is thus located near the magnetic head.
Thirdly, since the tension arm is a movable member which moves in response to a change in tension of the tape, it is difficult to design the tension arm so that it may maintain a proper vertical position. Accordingly, the tension arm is not contacted uniformly over the entire width with the tape, and hence the tape may possibly be displaced laterally in a widthwise direction. Besides, the tape may possibly have a warping habit.
Fourthly, since the support plate remains at its home position and is not at an advanced position while the tape feeding device is in a fast feeding (FF) mode or a rewinding (REW) mode, the tension arm on the support plate remains at a position spaced away from the tape. Consequently, an end of the tape cannot be detected. Accordingly, in the fast feeding mode or the rewinding mode of the tape feeding device, an automatic stopping operation cannot be effected. Meanwhile, even if an alternate construction is employed wherein the tension arm is contacted with the tape also while the tape feeding device is in the fast feeding mode or the rewinding mode, because the feeding speed of the tape is high in the fast feeding or rewinding mode and the tape tension is high accordingly, it is to difficult to detect arrival of an end of the tape as critically distinct from a high speed feeding of the tape. Accordingly, such a conventional automatic stopping mechanism as described above cannot be employed for detection of an end of a tape while the tape deeding device is in the fast feeding mode or in the rewinding mode.